INTRODUCTION: Dissemination of results of randomised controlled trials is traditionally limited to academic and professional groups rather than clinical trial participants. While there is increasing consensus that results should be communicated to trial participants, there is a lack of evidence on the most appropriate methods of dissemination. This study within a trial (SWAT) aims to address this gap by using a public and patient involvement (PPI) approach to identify, develop and evaluate a patient-preferred method of receiving trial results of the Thyroid Hormone Replacement for Subclinical Hypothyroidism Trial (TRUST). METHODS: An experimental (intervention) study will be conducted using mixed methods to inform the development of and evaluation of a patient-preferred method of communication of trial results. The study will involve three consecutive phases. In the first phase, focus groups of trial participants will be conducted to identify a patient-preferred method of receiving trial results. The method will be developed and then assessed and refined by a patient and public expert group. In the second phase participants will be randomly assigned to the intervention (patient-preferred method) and comparison groups (standard dissemination method as developed by the lead study site in Glasgow, Scotland). In the third phase, a quantitative questionnaire will be used to measure and compare patient understanding of trial results between the two groups. DISCUSSION: This protocol provides a template for other trialists who wish to enhance patient and public involvement and additionally, will provide empirical evidence on how trialists should best disseminate study results to their participants.